During hemofiltration, hemodialysis, hemodiafiltration, ultrafiltration, and other forms of renal replacement therapy, blood is drawn from a patient, passed through a filter, and returned to the patient. Depending on the type of treatment, fluids and electrolytes are exchanged in the filter between a dialysate and/or extracted from the blood by filtration. One effect may be a net loss of fluid and electrolytes from the patient and/or exhaustion of dialysate, with a concomitant need for its replenishment, again depending on the type of treatment. To replace fluid lost from the patient and keep the patient from dehydrating, replacement fluid may be injected into the patient at a rate that matches a rate of loss, with an adjustment for a desired net change in the patient's fluid complement. To replace exhausted dialysate, fresh dialysate is continuously circulated through the filter.
Presently methods to produce large volumes of dialysate from tap water are known, but each requires complex water purification and standardization equipment, since impurities and cleaning additives such as chlorine vary greatly in tap water from municipality to municipality and within a municipality over time. (See Twardowski U.S. Pat. Nos. 6,146,536 and 6,132,616.) Moreover, dialysate solution, whether prepared online or prepackaged, while of the proper concentration for use as a replacement fluid, is not directly infused into the patient's body. Instead, dialysate flows past a semipermeable membrane that permits ions and water to be exchanged across the membrane until a balance between their concentrations in blood and their concentrations in the dialysis is achieved. This is effective to remove impurities from the blood and to add missing electrolytes to the blood, but the volume of fluid that is infused is not as great as with hemofiltration.
Conventionally, dialysate and/or replacement fluid is supplied from either of two sources: batches of fluid, typically in multiple bags, or a continuous sources of water that is sterile-filtered and added to concentrated electrolytes to achieve the required dilution level. Because replacement fluid is injected directly into the patient, replacement fluid is required to be sterile and is recommended to have limited levels of pyrogens, particularly endotoxins, which are quantified in endotoxin units (EU). The maximum amount of endotoxin allowed in a parenteral product or medical device set by the US Food and Drug Administration (FDA) and United States Pharmacopoeia (USP) for drugs is 5.0 EU/Kg/hr, a rate taking into account the weight of the patient (in Kg.) and the rate of infusion. Currently, however, replacement fluid packaged such that it is regulated as a drug may have an endotoxin load of up to 0.5 EU/ml. This would limit the replacement fluid exchange rate for a 72 Kg. patient to less than 12 ml./min. To be safely infused, per these specifications, at higher rates, the fluid must be further filtered of endotoxins. Filtering to 0.03 EU/ml., a level that may be identified as “ultrapure,” allows an infusion rate of 200 ml./min., which may be sufficient for high rate continuous hemofiltration therapy of the type described in the following pending US patent applications each of which is hereby incorporated by reference as fully set forth in its entirety herein.
Ser. No. 08/800,881, filed Feb. 14, 1997 for Hemofiltration System;
Ser. No. 09/451,238 for Nov. 29, 1999 for Systems and Methods for Performing Frequent Hemofiltration;
Ser. No. 09/512,929, filed Feb. 25, 2000 for Fluid Replacement systems & Methods for Use in Hemofiltration;
Ser. No. 09/513,564, filed Feb. 25, 2000 for Systems and Methods for Detecting Air in an Arterial Blood Line of a Blood Processing Circuit;
No. 60/438,567, filed Jan. 30, 2003 for Preparing Replacement Fluid by Means of Batch Filtration Prior to Treatment;
Ser. No. 09/513,910, filed Feb. 25, 2000 for Systems and Methods that Maintain Sterile Extracorporeal Processing Conditions;
Ser. No. 09/513,911, filed Feb. 25, 2000 for Synchronized Volumetric Fluid Balancing Systems and Methods;
Ser. No. 09/513,915, filed Feb. 25, 2000 for Systems and Methods for Controlling Blood Flow & Waste Fluid Removal During Hemofiltration;
Ser. No. 09/862,207, filed May 21, 2001 for Methods, Systems and Kits for the Extracorporeal Processing of Blood;
Ser. No. 09/865,905, filed May 24, 2001 for Fluid Processing Systems and Methods Using Extracorporeal Fluid Flow Panels Oriented Within a Cartridge;
Ser. No. 09/894,236, filed Jun. 27, 2001 for Hemofiltration System;
Ser. No. 09/900,362, filed Jul. 7, 2001 for Method and Apparatus for Leak Detection in a Fluid Line (Disconnect Sensor—Reverse Lines to Use Air Sensor on Arterial Line (Leak));
Ser. No. 09/905,246, filed Jul. 12, 2001 for Devices and Methods for Sterile Filtering;
Ser. No. 09/907,872, filed Jul. 17, 2001 for Hermetic Flow Selector Valve;
Ser. No. 60/324,437 filed Sep. 24, 2001 for Device and Method for Enhancing Performance of Membranes.
Ser. No. 10/040,659, filed Jan. 7, 2002 for Blood Treatment Replacement Fluid Using Infusible Fluids in Combination;
No. 60/346,458 filed Jan. 7, 2002 for Hemofiltration Filter with High Membrane Utilization Effectiveness; and
No. 60/346,403 filed Jan. 7, 2002 for Hemofiltration System Method of Use and Associated Control System.
In many instances, blood treatment therapies may require a large quantity of sterile fluid. A typical way to provide the large quantity of replacement fluid is to provide multiple bags of replacement fluid, dialysate, or infusate. The connection of these bags of fluid to an extracorporeal blood circuit creates a risk of touch contamination resulting in the introduction of contaminants into the fluids. Contamination may occur, for example, at the point where bags of fluid are accessed (“spiked”) or at other times during preparation for infusion such as when the patient is accessed.
Attempts to render dialysate suitable for use as a replacement fluid in hemofiltration and hemodiafiltration have focused on continuous sterilization processes that require a separate dialysate filtration/purification apparatus that must be periodically purged and verified to provide sufficient constant flow of sterile replacement fluid required for hemofiltration. (See Chavallet U.S. Pat. Nos. 6,039,877 and 5,702,597.) Such devices are necessarily complicated and require separate pumping systems for the sterilization process. In addition, the rate of supply of dialysate for such systems is very high, requiring an expensive filter to be used. The same high-rate problem exists for the generation of replacement fluid for hemofiltration, and therefore also requires an expensive filter.
There is a need for improved mechanisms for providing safe economic replacement fluid for use in various blood therapies.